Answer(x,y,z) ← R(x,y,z) AND x ≥ y AND x ≥ z Answer(x,y,z) ← R(x,y,z) AND y ≥ z
Exercise 5.4.3a
Answer(a,b,c,d) ← R(a,b,c) AND S(b,c,d)
Exercise 5.4.3b
Answer(b,c,d,e) ← S(b,c,d) AND T(d,e)
Exercise 5.4.3c
Answer(a,b,c,d,e) ← R(a,b,c) AND S(b,c,d) AND T(d,e)
Exercise 5.4.4
a) Answer(rx,ry,rz,sx,sy,sz) ← R(rx,ry,rz) AND S(sx,sy,sz) AND rx = sy
b) Answer(rx,ry,rz,sx,sy,sz) ← R(rx,ry,rz) AND S(sx,sy,sz) AND rx < sy AND ry < sz
c) Answer(rx,ry,rz,sx,sy,sz) ← R(rx,ry,rz) AND S(sx,sy,sz) AND rx < sy Answer(rx,ry,rz,sx,sy,sz) ← R(rx,ry,rz) AND S(sx,sy,sz) AND ry < sz
d) Answer(rx,ry,rz,sx,sy,sz) ← R(rx,ry,rz) AND S(sx,sy,sz) AND rx = sy
e) Answer(rx,ry,rz,sx,sy,sz) ← R(rx,ry,rz) AND S(sx,sy,sz) AND rx = sy Answer(rx,ry,rz,sx,sy,sz) ← R(rx,ry,rz) AND S(sx,sy,sz) AND ry ≥ sz
f) Answer(rx,ry,rz,sx,sy,sz) ← R(rx,ry,rz) AND S(sx,sy,sz) AND rx ≥ sy AND rx ≥ sz Answer(rx,ry,rz,sx,sy,sz) ← R(rx,ry,rz) AND S(sx,sy,sz) AND ry ≥ sz
Exercise 5.4.5a
R1 := πx,y(Q R)
Exercise 5.4.5b
R1 := ρR1(x,z)(Q) R2 := ρR2(z,y)(Q)
R3 := πx,y(R1 (R1.z = R2.z) R2)
Exercise 5.4.5c
R1 := πx,y(Q R) R2 := σx < y(R1)